Canberra
3.1 Urban water supply system

This line item refers to the volume of water held in ACTEW's potable and non-potable water supply system. There are 47 tanks (service reservoirs) within ACTEW's supply system and approximately 3,140 km of pipes.

This volume is expected to remain relatively constant each year, with slight increases in pipe network volume due to the expansion of the network, and slight changes in the tank (service reservoir) volumes due to operational level changes.

Urban water supply system for the Canberra region

	ACTEW (ML)	QCC (ML)
Pipes	273	NA
Tanks	580	NA
Subtotal	853	NA
Total	853

QCC = Queanbeyan City Council; NA = Data not available for QCC supply system.

ActewAGL: Water Data Warehouse (service reservoir data) ActewAGL: geographic information system (GIS) database (pipe data)

ActewAGL.

The volume in the tanks (service reservoirs) was reported as the volume at 8 am 1 July 2010 and 1 July 2011. The volume in the pipe network was calculated based on the pipe lengths and nominal internal pipe diameters as recorded in the GIS database, assuming all the pipes were full. This includes both non-potable and potable water pipes.

These data does not include service water storages or the pipe network managed and owned by Queanbeyan City Council (QCC). The QCC water supply system is much smaller in size than the ACTEW system and it is expected that the volume stored within the QCC tanks and pipes would be much less than that reported for ACTEW's system.

Data are measured, uncertainty is estimated at +/– 10%.

This line item corresponds to Line Item 5.1 Urban potable water supply system, reported in the 2010 Account. The following table presents substantive changes to the 2009–10 volume reported in the 2011 Account with the corresponding line item in the 2010 Account. The reasons for the changes, with their respective values, are detailed in the table and summarised hereafter: data are now available to estimate this volume. Given the minor change in volume that occurs from year to year within potable pipe networks, the National Water Account 2010 closing balance volumes were amended with these new data. These changes are summarised in the following table.

Comparative year information – Line Item 3.2 Urban water supply system

Corresponding  2010 Account line item	Component	Value reported for the 2010 Account closing balance (ML)	Value difference due to scope change (ML)	Reported in the 2011 account for the 2010 account closing balance (ML)
Line item 5.1 Urban potable water supply system	Pipes	0	273	273
	Tanks	612	0	612
	Total	612	273	885